![]() ![]() The Ec and Ev of the semiconductor also bend down following the principals of MS contact. From the band diagram view, the applied bias lowers the Fermi level of the metal below the Fermi level of the semiconductor. This happens for n-type semiconductor when V G >0. The first type of biasing region is accumulation, where the majority carrier concentration is greater near the oxide-semiconductor interface than in the bulk of the semiconductor.Therefore, the V G can be calculated as the equation (1) shown below, where q is the electric charge. One thing worth mentioning is that the Fermi level of semiconductor does not change when V G is applied. Since the focus is the mechanisms under biasing conditions, the p-type diagrams follow the same concepts but are not discussed here. However, the types of biasing regions are also different from n-type and p-type semiconductor because of the different positions of the Fermi level as well as the doped charges. Three different types of biasing regions with different shape of both energy band and corresponding block charge diagram occur and they are showed in figure 3, 4, 5 and 6 below for n-type semiconductors. Other than the flat band in the MOS structure, as the d.c bias VG apply to the MOS-C devices. Figure 2 (a) The flat band diagram of MOS-C in equilibrium with n-type semiconductor, (b) the block charge diagrams of flat band MOS-C. The region above X-axis is the positive charge Q which is created by holes concentration, while the region below X-axis is the negative charge Q which is created by electrons concentration. There are two horizontal Y-axis which represent the metal-oxides interface and oxide-semiconductor interfaces. However, the Y-axis represents the exact charge distribution Q in the MOS devices. Like the energy band diagram, the X-axis represents the distance (x) in the cross-section view. The block charge diagram shows the charge density distribution inside the MOS structure. Since there are no charge or electric field in the flat band MOS-C device, the inserted insulator can only have an effect in slightly lowering the energy barrier and there is no block charge diagram for flat band like figure in 2(b). The formation of this band diagram can conceptually think of the equilibrium metal-semiconductor contact but is separated with a distance x0, the thickness of the oxide layer.The Fermi level aligned between metal and semiconductor since it's specified in the property 8 above. The zero-bias band diagram in figure 2 (a) is called flat band diagram. The electron affinity (X) specifies the height of energy barrier in semiconductors, so the X i is the energy barrier of the insulator (oxides SiO 2). The work function ΦM and ΦS are the amount of work to remove an electron, so it's the difference between Fermi level (E F) and E vc. The E vc is the vacuum level which is th minimum energy an electron must reach in order to free from the material. In the figure 2 below is the energy band diagram of MOS-C in flat band with n-type semiconductor. As the Y-axis is increasing, the corresponding energy is higher. There are no arbitrary values for Y but only relative values. The X-axis represents the distance (x) in the cross-section view of the MOS devices. The band diagram shows the band energy of the materials and how their energy levels change in the process as functions of spatial dimensions. Being certified as an MOS Master demonstrates you have the deepest level of skills needed to proficiently use key Office programs.\): The schematic of an ideal MOS-C device MOS Master-Pass exams in Word or Excel to earn a Microsoft Office Specialist Master certification. Being certified as an MOS Expert demonstrates you have advanced skills in key Office programs.įind training and earn an MOS Expert certification MOS Expert-Pass exams in Word or Excel to earn a Microsoft Office Specialist Expert certification. ![]() Find training and earn a MOS certification in: ![]() Being certified as a Microsoft Office Specialist demonstrates you have the skills needed to get the most out of Office. Microsoft Office Specialist-Pass an exam in a specific Office program to earn a Microsoft Office Specialist certification. ![]()
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